Rotary driven variable resistor

ABSTRACT

A rotary driven variable resistor comprises a casing, a screwthreaded shaft rotatably mounted in the casing, a resistance element disposed longitudinally in the casing, and a sliding contact positioned in the casing and on the resistance element. The sliding contact is made of a resilient metal plate and is formed into an upper surface plate and a contact plate integrally connected together. The upper surface plate has a reversed channel configuration and is partly cut out to provide a centrally located projection engageable with the screw-threaded shaft. The contact plate is bent back downwardly and formed into an inverted chevron shape with at least one contact formed on the rear side of the apex portion, so that when a free end of the contact plate resiliently abuts an end of the upper surface plate, a well balanced spring force is applied to the contact.

United States Patent t191 Aoki l tu] 3,815,076 [45] June'4, '1974 [54] ROTARY DRIVEN VARIABLE RESISTOR [75] Inventor: Masatsugu Aoki, Soma, Japan [73] Assignee: Alps Electric Co. Ltd., Tokyo, Japan [22] Filed: May 2l, 1973 [2l] Appl. No.: 362,351

Primary Examiner-Bernard A. Gilheany Assistant Examiner-David A. Tone Attorney, Agent, ar Firm-Eliot S. Gerber [57] f ABSTRACT A rotary driven variable resistor comprises a casing, a screw-threadedshaft rotatably mounted ,in the casing, a resistance element disposed longitudinally in the casing, and a sliding Contact positioned in the casing and on the resistance element. The sliding contact is made of a resilient metal plate and is formed into an upper surface plate and a contact plate integrally connected together. The upper surface plate has a reversed channel configuration and is partly cut out to provide a centrally located projection engageable with the screw-threaded shaft. The contact plate is bent back downwardly and formed into an inverted chevron shape with at least one Contact formed on the rear side of the apex portion, so that when a free 'end of the Contact plate resiliently abuts an end of the upper surface plate, a well balanced spring forceis applied to the. contest.. Y.

7 Claims, 4 Drawing Figures ROTARY DRIVEN VVARIABLE RESISTOR BACKGROUND OF THE INVENTION This invention relates generally to rotary driven variable resistors, and more particularly to a type thereof resistors, including those having a lineally driven sliding contact, have been proposed. However, except in large precision type instruments most of the conventional rotary driven variable resistors have not been satisfactory because of the excessive allowance and play existing in the engagement betweenl the sliding contact and the driving shaft and the lack of reliable guidance for the movement of the sliding contact. Furthermore, so far as Iam aware, none of-the conventional rotary driven variable resistors of small size have been provided with a protection against excessive drive of the sliding contact. L l

A primary objective of the presentvinvention is to provide a rotary driven variable resistor wherein allowance or play in the engagement between the sliding contact and the driving shaft are minimized, and the movement of the sliding contact is thereby stabilized.

SUMMARYl OF THE INVENTION The above-mentioned and otherobjectives of the present invention can be achieved vby a rotary driven variable resistor which comprises a casing, a screwthreaded shaft rotatably mounted in said casing, a resis. tance `element disposed on the bottom of the casing, and a sliding contact. The sliding contact is made of a FIG. l is a longitudinal sectional view of a rotary driven variable resistor constituting a preferred embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along the line A`A in FIG. l;

FIG. 3 is a perspective view of a sliding contact which constitutes an important part of this invention; and

FIG. 4 is a side elevational view of the sliding contact.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIGS. l and 2, there is indicated a rotary driven variable resistor which comprises a casing l, a resistance element 2 secured on the bottom plate of the casing l, a screw-threaded shaft 3 freely rotatably mounted in the casing l, and la sliding contact .4 which is driven by the rotation of the screw-threaded shaft 3 to move along the resistance element 2 in a sliding manner. In this example, a gearwheel 5 is secured to the exposed end of the screw-threaded shaft 3, which shaft 3 passes through an end wall of the casing l. A rotating movement may be transmitted through the gear wheel 5 to the screw-threaded rotatable shaft 3. A required number of terminals 6, 6, are also provided through the bottom wall of the casing l.

As is clearly indicated in FIGS. 3 and 4, the sliding contact 4 is made of a resilient metal plate which. is formed to provide a reversed-channel shaped upper surface plate 7 anda contact plate l0 integrally connected to one end of the upper surface plate 7. The upper surface plate 7 has four supporting legs 9 forward and backward on both sidesthereof and is partly punched out at 7a so that a central projection-8 is established perpendicular to the upper surface of the lupper surface plate 7.

Inwardly of the'sliding contact 4 on the rear side of the upper surface plate 7, the contact plate l0 is bent back to form a reversed triangular or chevron shape,

and two contacts ll are formed on the rear side of the apex portion of the reversed triangular shaped contact plate l0.

When the sliding contact 4 is placed interior of the casing l with the central projection 8 engaged with the valley of the screw thread on theshaft 3, a free end 10a of the contact plate 10 abuts against the rear side of the upper surface plate 7, as best indicated in FIG. 4. This resilient metal plate which is formed to `provide a reversed channel shaped upper surface plate and a contact plate integrally connected to one end of said upper surface plate, said upper surface plate being partly cut out thereby to form a central projection en gaging with said screw-threaded shaft. The contact plate is bent back downwardly into a reversed triangular shape with at least one contact, and preferably two, formed on the rear side of the apex portion of the contact plate such that the contact is brought into contact with said resistance element, and a free end of said contact plate resiliently abuts against the other end of the upper surface plate.

The nature, principle, and utility of the present invention will bevmore fully understood from the following detailed description of theinvention when read in conjunction with the accompanying drawing wherein like parts are designated by like reference numerals.

In the drawing:

constriction provides a well balanced resilient force for the contact ll contacting the resistance element 2 on the bottom plate of the casing l.

Furthermore, as best indicated in FIG. 2, guiding steps la, la are provided on the inner surfaces of the two longitudinal walls of the vcasing I'thereby to prevent any malfunctioning displacement of the sliding contact 4 in the vertical direction while the sliding contact4 is driven along the resistance element 2 in the casing l.

On the end of the upper surface plate 7 of the sliding contact 4,'two holes 12, l2 are provided on both sides thereof, and these holes may be utilized for securing an attachment I3, such as an indicator,'to the upper surface plate as indicated by broken lines in FIG. l.

Since the rotary driven variable resistor according to the present invention is constructed as described above, the uprising projection 8 and the contact ll'of the sliding contact 4 are both under the action of spring forces against the screw-threaded shaft 3 and theresistance element 2, respectively. The spring force acting on the contact ll is well balanced with respect toa vertical line passing through the contact 1l because the as described above, the transversal and longitudinal deviations of the sliding contact which have frequently occurred in the conventional rotary driven variable resistors can be substantially eliminated and a stable and accurate operation are assured.

l claim:

l. A rotary driven variable resistor comprising a casing, a screw-threaded shaft rotatably mounted in the casing, a resistance element disposed longitudinally on the bottom of the casing, and a sliding contact placed on the resistance element and driven by said screw-` threaded shaft along the resistance element wherein said sliding contact is of a resilient metal plate formed into a reversed-channel shaped upper surface plate and a' contact plate integrally connected together, said upper surface plate` being partly cut out thereby to obtain a centrally located projection engageable with said screw-threaded shaft, said contact plate being bent back downwardly and formed into an inverted chevron-like configuration with at least a contact formed on the rear side of the apex, and a free end of said contact plate resiliently abuting an end of said upper surface plate, to provide a well balanced spring force to the contact slidably contacting said resistance element.

2. A rotary driven variable resistor as set forth in claim 1 wherein said upper surface plate formed into a reversed-channel configuration has two side walls slidably abutting against two inner walls of the casing.

3. A rotary driven variable resistor as set forth in claim 2 wherein a guiding step is provided in each of the two inner walls of the casing, and said two side walls of the upper surface plate are guided on said two guiding s teps.

4. A rotary driven variable resistor as set forth in claim l wherein said centrally located projection of the sliding contact is engaging with a valley of said screwthreaded shaft.

5. A rotary driven variable resistor as set forth in claim l wherein a required number of terminals are provided through this bottom wall of the casing.

6; A rotary driven variable resistor as set forth in claim l wherein a pair of holes are further provided in the upper surface plate, and an indicator is secured to the upper surface plate utilizing said two holes.

7. A rotary driven variable resistor as set forth in claim l wherein two contacts aligned transversely are provided on the rear side of the apex of the inverted chevron-like contact plate.

l vO Ik 

1. A rotary driven variable resistor comprising a casing, a screw-threaded shaft rotatably mounted in the casing, a resistance element disposed longitudinally on the bottom of the casing, and a sliding contact placed on the resistance element and driven by said screw-threaded shaft along the resistance element wherein said sliding contact is of a resilient metal plate formed into a reversed-channel shaped upper surface plate and a contact plate integrally connected together, said upper surface plate being partly cut out thereby to obtain a centrally located projection engageable with said screw-threaded shaft, said contact plate being bent back downwardly and formed into an inverted chevron-like configuration with at least a contact formed on the rear side of the apex, and a free end of said contact plate resiliently abuting an end of said upper surface plate, to provide a well balanced spring force to the contact slidably contacting said resistance element.
 2. A rotary driven variable resistor as set forth in claim 1 wherein said upper surface plate formed into a reversed-channel configuration has two side walls slidably abutting against two inner walls of the casing.
 3. A rotary driven variable resistor as set forth in claim 2 wherein a guiding step is provided in each of the two inner walls of the casing, and said two side walls of the upper surface plate are guided on said two guiding steps.
 4. A rotary driven variable resistor as set forth in claim 1 wherein said centrally located projection of the sliding contact is engaging with a valley of said screw-threaded shaft.
 5. A rotary driven variable resistor as set forth in claim 1 wherein a required number of terminals are provided through this bottom wall of the casing.
 6. A rotary driven variable resistor as set forth in claim 1 wherein a pair of holes are further provided in the upper surface plate, and an indicator is secured to the upper surface plate utilizing said two holes.
 7. A rotary driven variable resistor as set forth in claim 1 wherein two contacts aligned transversely are provided on the rear side of the apex of the inverted chevron-like contact plate. 